Fix timeouts in group autocomplete query

What does this MR do and why?

When fix_user_authorized_groups is enabled, the autocomplete query can result in a bad query plan where PG does an index scan on the routes table.

We fix this by wrapping the groups in a materialized CTE which then gets filtered by the route pattern.

Queries

• Old: https://postgres.ai/console/gitlab/gitlab-production-main/sessions/32239/commands/99632
• New: https://postgres.ai/console/gitlab/gitlab-production-main/sessions/32239/commands/99631

MR acceptance checklist

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Related to #482866 (closed)